You may change the Debtor group 1 and / or 2  for selected debtor (customer / client) account(s). 

To change the Debtor group 1 or 2: 

1.On the Debtors (Debtors list) (Action ribbon), select the debtor (customer / client) account(s).

If you need to select multiple debtor (customer / client) account(s), press the Ctrl or Shift key and click on each debtor (customer / client) account, for which you need to change the debtor reporting group.

2.Right-click and select "Debtor group 1" or "Debtor group 2" on the context menu. 

3.Select "Empty" or the available debtor group from the sub-menu. The "Debtor group 1" or "Debtor group 2" will change on reports.